System for unsticking pipes of a drill string of a drilling apparatus

ABSTRACT

An unstuck system of stuck drill pipes of a drill string of a drilling apparatus adapted to drilled wells to extract fluids or mud includes a torsion coupling system adapted to disconnect an upper portion from a bottom portion including the stuck drill pipes of the drill string and to transfer a rotation to the unstuck system. The unstuck system includes at least an axial forced vibration generator including at least one axially movable element adapted to generate at least a vibration which is propagated to pipes of a portion free from being stuck, where the induced vibrations fall within a band of induced frequencies near or corresponding to a resonance frequency of the portion free from being stuck.

The present invention refers to a system for unstucking pipes of a drill string of a drilling apparatus.

In the state of the art, systems are known for unstucking pipes of a string of hollow tubular pipes of a drilling apparatus comprising a rotating drill bit adapted to drill wells in soil to extract fluids or mud, for example hydrocarbons. The pipes may be stuck in rotation when stuck in the surrounding soil of the well, thus preventing the drilling apparatus from proceeding to drill the well.

A drill pipe unstucking system is known in the jargon as a “jar” and comprises a spindle, a hammer slidably associated to a hollow collar of a diameter comparable to that of a tubular pipe and at least one anvil on which the axial force of the hammer is discharged. The “jar” is assembled in depth to one end of the tubular drill string between heavy pipes (“drill collar” in the jargon) and the drill bit. The “jar” comprises an elastic system adapted to free the stored energy or free a pressure energy of a fluid and is adapted to develop a very intense force impulse directed in axis with the pipes in the direction of the drill bit but disadvantageously of a short duration.

Disadvantageously the pipe unstucking apparatus cannot express great power for a long time, and therefore does not guarantee the unstucking of all the drill pipes in the string, often forcing some of the pipes in the string and the drill bit to be abandoned in the well. Disadvantageously it is then necessary to drill another well.

Other systems for unstucking pipes are known, comprising a fishing drill string, but disadvantageously these systems are not assembled at a depth along with the tubular drill string near the drill bit, and must therefore be taken to the well bottom later, wasting more time and meanwhile risking the consolidation of the soil around the stuck pipes.

The object of the present invention is to implement a system for unstucking the pipes in a tubular drill string of a drilling apparatus for drilling wells in soil which overcome the disadvantages of the prior art.

According to the invention, this object is achieved by a system for unstucking pipes in a drilling apparatus for drilling wells in soil to extract fluids according to claim 1.

Another object of the present invention is to implement a process for unstucking the pipes in a tubular drill string of a drilling apparatus for drilling wells in soil which overcome the disadvantages of the prior art.

According to the invention, this object is achieved by a process for unstucking pipes in a drilling apparatus for drilling wells in soil to extract fluids according to claim 18.

Other characteristics are envisaged in the dependent claims.

The features and advantages of the present invention will be more apparent from the following description, which is to be understood as exemplifying and not limiting, with reference to the appended schematic drawings, wherein:

FIG. 1 is a view of a bottom portion of a string of hollow tubular pipes of a drilling apparatus according to the present invention;

FIG. 2 shows a perspective view of a partial section of an unstuck system of the drilling apparatus comprising an impulsive axial forced vibration generator;

FIG. 3A shows the unstuck system in FIG. 1 during the loading step of an elastic element with a hammer lifted by an anvil element;

FIG. 3B shows the unstuck system in FIG. 1 during the unloading step of an elastic element with a hammer hitting the anvil element;

FIG. 4 shows a partial section of an unstuck system according to an alternative comprising an impulsive axial forced vibration generator with a number of hammers corresponding to number of elastic elements;

FIG. 5A shows the unstuck system in FIG. 4 during the loading step of one of the many elastic elements with one of the hammers lifted by an anvil;

FIG. 5B shows the unstuck system in FIG. 4 during the unloading step of the elastic element in FIG. 5A where the hammer in FIG. 5A hits the anvil;

FIG. 6 shows a partial section of an unstuck system according to an alternative embodiment including an axial forced periodic vibration generator;

FIG. 7 shows a partial section of an unstuck system device according to an alternative embodiment including an alternative periodic axial forced vibration generator;

FIGS. 8A-8D show the phases of entry and exit from the chambers of an annulus of the alternative unstuck system in FIG. 7;

FIGS. 9A-9C show a series of section figures of an alternative unstuck system including an alternative periodic axial forced vibration generator;

FIGS. 10A-10C show a series of section figures of an alternative unstuck system including an alternative periodic axial forced vibration generator;

FIGS. 11A-11C show a series of section figures of an alternative unstuck system including an alternative periodic axial forced vibration generator;

FIGS. 12A-12D show a series of section figures of an alternative unstuck system including an alternative periodic axial forced vibration generator;

FIGS. 13A-13C show a series of section figures of an alternative unstuck system including an alternative periodic axial forced vibration generator;

FIGS. 14A-14E show a series of section figures of an alternative unstuck system including an alternative periodic axial forced vibration generator;

FIGS. 15A-15C show a series of section figures of an alternative unstuck system including an alternative periodic axial forced vibration generator;

FIGS. 16A-16C show a series of section figures of an alternative unstuck system including an alternative periodic axial forced vibration generator.

With reference to the above-mentioned figures, a drilling apparatus 100 is shown comprising a hollow tubular drill string 20, an unstuck system 10 for unstucking a rotation of the hollow tubular pipes 20 of the drill string 20, a drill bit 30 and a bottom end which placed in rotation is adapted to drilled wells in soil to extract fluids or mud, for example hydrocarbons.

The drilling apparatus 100 also comprises a head motor, not shown in the figures as it is on the surface, which transmits the rotation to a number of drill pipes 20 in line which form the hollow tubular drill string 20. This rotation is used to transmit all the power available from the surface to the bottom of the well. The unstuck system 10 is arranged in line with the drill string 20 at the bottom portion 23 (“Bottom Hole Assembly” in the jargon) of the drill string 20.

Advantageously the unstuck system 10 arranged in axis with the bottom portion 23 of the drill string 20 allows to act promptly in order to free stuck drill pipes 25 in the bottom portion 23 of the drill string 20. The stuck drill pipes 25 are drill pipes 20 of the bottom portion 23 where at least one portion is stuck in its rotational and translational movement, being stuck in a part of the surrounding soil of a drilled well.

The drilling apparatus 100 comprises a torsion coupling system 40 adapted to disconnect, only tortionally, an upper portion 21 of the drill string 20 from the bottom portion 23 of the string comprising the stuck drill pipes 25.

The torsion coupling system 40 is arranged above an upper end of the bottom portion 23 of the drill string 20 and beneath a bottom end of the upper portion 21 of the drill string 20, joining the upper portion 21 with the lower portion 23 of the drill string 20.

The unstuck system 10 is assembled in order to be as distant as possible from the drill bit 30, but associated to the bottom portion 23 of the drill string 20.

Advantageously the unstuck system 10 is assembled near the torsion coupling system 40.

The axial force, for example traction, can be generated for example by the head motor of the system on the surface. In other words, the torsion coupling device 40 must not only let the part of the string above it free to rotate in order to transmit to the unstuck system 10 the power generated for example by the head motor but also to guarantee the transfer of the axial force to the stuck drill pipes 25. The unstuck system 10 generates forces the effect of which are added to that of the static axial force generated for example by the head motor on the system on the surface. In other words, the forces generated by the unstuck system 10 have an average value equal to the axial force, where such average value may obviously be also zero).

These vibrations act directly on the stuck area, not only to try to overcome the reaction force but also to try to alter its mechanical characteristics, thus reducing the reaction force, for example by inducing phenomena such as softening.

The unstuck device 10 is mounted in axis with the bottom portion 23 of the drill string 20.

The unstuck system 10 passes from a step of inactivity to a step of activity when it is activated to unstuck the stuck pipe 25.

The unstuck system 10 is activated outside of the well, from the surface, by means of suitable tractions of the drill string 20 or by means of the release of appropriate balls which drop or are pushed into the internal cavity of the pipes 20 in the drill string 20 or hydraulically by means of the drilling mud, or by a combination of the above-described activation methods.

To pass from the step of inactivity to the step of activity the bottom portion 23 of the drill string 20 mounting the unstuck system 10 is released from the rotation of the upper portion 21 of the drill string 20 by means of the torsion coupling system 40, thus freeing the unstuck system 10 from rotation.

Once the unstuck system 10 is activated by the freeing of the torsion coupling, the torsion coupling system 40 transfers the mechanical power to the unstuck system 10, i.e. for example the torque and the rpm made available by the head motor.

The unstuck devices 10 comprises an axial forced vibration generator 11 which generates axial forces when the unstuck device 10 is in the step of activity. The axial forces generated by the axial forced vibration generator 11 are such that they act directly on the bottom portion 23 of the drill string 20 which comprises the stuck drill pipes 25.

The axial forced vibration generator 11 of the unstuck system 10 generates axial forces which produce vibrations in a range of frequencies ν_(A).

The axial forced vibration generator 11 of the unstuck system 10 varies the band of frequencies ν_(A) within a set frequency range which depends on the geometry of the bottom portion 23 of the drill string 20. Depending on the geometry of the bottom portion 23 of the drill string 20 in this embodiment, the range of frequencies ν_(A) lies between 0 and 30 Hz.

The axial forced vibration generator 11 of the unstuck system 10 advantageously also produces harmonic vibrations.

The said vibrations generated by the axial forced vibration generator 11 propagate to a portion free from stuck 24 between the torsion coupling system 40 and the stuck drill pipes 25 in the bottom portion 23 of the drill string 20, generating induced vibrations. The induced vibrations in the portion free from stuck 24 lie within a band of induced frequencies ν_(F) near or corresponding to a resonance frequency ν₀ of the portion free from stuck 24, the ideal condition for advantageously amplifying the force and further induced vibrations on the stuck drill pipes 25.

The induced vibrations of the portion free from stuck 24 propagate further into the surrounding soil through the stuck drill pipes 25.

Advantageously the unstuck system 10 alters the mechanical characteristics of the surrounding soil reducing the reaction force and inducing phenomena such as soil “softening”.

Advantageously the generation of the axial forces by the axial forced vibration generator 11 ends automatically as soon as the stuck drill pipes 25 are freed from the surrounding soil.

It is envisaged that the unstuck system 10 according to the present invention comprises two types of axial force generators 11: impulsive axial force generators 12 shown in FIGS. 2-5 and periodic axial force generators 13 shown in FIGS. 6-16.

As shown in FIGS. 2-5 the impulsive axial force generators 12 comprise one or more mobile components, for example the hammers 50, which move with alternate motion compressing one or more elastic means 70, such as for example springs. The hammers 50 discharge their power on an anvil element 26 which is a portion of a drill pipe 20 of the bottom portion 23 of the drill string 20. The elastic energy stored in these elastic means 70 is exploited to generate impulses generated by the impact between the hammers 50 and the anvil element 26 propagating the impulse and the vibrations to the stuck drill pipes 25.

The hammer 50 is charged by a purely mechanical system comprising an internal rotating shaft 60 comprising at least one protruding periodic profile 65 which is helical in shape and above which there is at least one sliding coupling cam 55 which is connected to the hammer 50 or is a portion of the hammer 50. The profile 65 is used to define the type of motion to which the hammer 50 is subjected.

The internal rotating shaft 60 is moved by means of the torsion coupling system 40 which, releasing the rotation of the upper portion 21 from the bottom portion 23 of the drill string 20, transmits the rotation to the internal rotating shaft 60 by means of a grooved profile 61 to a bottom portion of the internal rotating shaft 60 which is a lower shaft 62 which is inside a drill pipe 20 which mounts the unstuck system 10. The rotational movement is therefore directly transmitted by the head motor or other plant on the surface, after the torsion coupling system 40 has released the bottom portion 23 of the drill string 20.

It is possible to provide for the rotation of the internal rotating shaft 60 transmitted also or alternatively by a motor on the well bottom, such as a turbine. It is possible to provide for the turbine or motor on the well bottom mounted with the unstuck system 10.

As shown in FIGS. 2 and 3 the unstuck system 10 is mounted in a drill pipe of the bottom portion 23 of the drill string 20 and comprises the internal rotating shaft 60, the hammer 50, the anvil element 26 and the elastic means 70.

The internal rotating shaft 60 comprises an upper portion 64, the grooved profile 61 and a bottom portion which is the lower shaft 62. The upper portion 64 of the internal rotating shaft 60 is connected by means of the grooved profile 61 to the lower shaft 62. The internal rotating shaft 60 is hollow and tubular so that the mud from the drilled well can pass through. The internal rotating shaft 60 is mounted inside a drill pipe 20 of the drill string 20.

The upper portion 64 of the internal rotating shaft 60 is connected to the torsion coupling system 40. When there are stuck drill pipes 25, i.e. some of the pipes 20 of the bottom portion 23 of the drill string 20 are blocked by the soil surrounding the drilled well, then the torsion coupling system 40 transfers the rotational movement from the drill pipes 20 to the internal rotating shaft 60 which is inside them.

The internal rotating shaft 60 comprises a protruding periodic profile 65. Corresponding to this periodic profile 65 a hammer 50 is slidably assembled with the drill pipe 20 inside the drill pipe 20 itself. The hammer 50 is a hollow cylinder concentric to the rotating shaft 60 comprising a cam 55 which extends outside the hammer 50 between an external surface of the hammer 50 and an internal surface of the drill pipe 20. The cam 55 is adapted to sliding above the helical profile 65 of the shaft 60 making the hammer 50 move upwards following the shape of the periodic profile 65. The periodic profile 65 has an interrupted helical shape and comprises a bottom portion and an upper portion at two different heights, where the height is measured from the well bottom following a central axis of the drill string 20. During the rotation of the shaft 60, the cam 55 is guided by the periodic profile 65 in rotation, i.e. as shown in FIGS. 2-3, the cam 55 of the hammer is guided rising above the bottom portion of the periodic profile 65. During rotation the cam 55 follows the periodic profile 65 until it reaches the upper portion of the profile 65 at a higher level than the bottom portion. At this point the cam 55 falls downwards taking the hammer 50 with it, which falls above the anvil element 26 which is a portion of the drill pipe 20. The impulse and the vibration of the hammer 50 are transmitted to the drill pipe 20 propagating as far as the stuck drill pipes 25 and propagating in the surrounding soil.

The periodic profile 65 is protruding, as shown in FIGS. 2-3.

The elastic means 70 are mounted between the hammer 50 and a seat 27 of the drill pipe 20. The seat 27 is a part of the unstuck system 10.

The seat 27 shown in FIGS. 2-3 is a groove, but alternatively it is also possible to use a seat 27 which is a protrusion.

The elastic means 70 are used to push the hammer 50 towards the anvil element 26 with greater force. The elastic means 70 are in fact adapted to pass from a position of compression as shown in FIG. 3A to a position of relaxation, as shown in FIG. 3B where the elastic means 70 push the hammer 50 towards the anvil element 26.

The anvil element 26 is the upper portion of the drill pipe 20 lower than that on which the impulsive axial force generator 12 is mounted.

The unstuck system 10 also comprises thrust bearings 80 mounted above the elastic element 70 between an upper portion of the elastic element 70 and the seat 27 of the drill pipe 20 which also acts as the seat for these thrust bearings 80. These thrust bearings 80 are used to obtaining greater resistance of the unstuck system 10 mounted with the drill pipe 20.

The frequency of the impacts between the hammer 50 and the anvil element 26 is proportional to the number of turns of the upper portion 21 of the drill string 20, the number of interruptions of the periodic profile 65 and the number of unstuck systems 10 used in series. The amplitude of the impulse is proportional to the rigidity of the elastic means 70 and the extent of the mass of the hammer 50.

The torsion coupling system 40 transmits a constant static load axial load to the bottom portion 23 of the drill string 20.

An application to the drill string 20 of the traction or compression static axial load produces an effect which overlaps with that of the axial forces generated by the axial forced vibration generator 11 of the unstuck system 10. The static axial load is generated by the head motor, or by another surface-mounted device of the drilling apparatus 100.

The generation of this static axial load ends when the stuck drill pipes 25 of the drill string 20 are released.

Advantageously the unstuck system 10 allows a reduction in well drilling times by reducing the time to free the stuck drill string 20, thanks to an increase in operational safety when actions linked to the removal of the drill string and the use of the retrieval string are avoided.

Alternatively it is possible to envisage that the drilling apparatus 100, in addition to the head motor, also comprises at least one other motor on the well bottom, not shown in the figures, which even more advantageously transmits more rotational power to the hollow tubular drill string 20.

Alternatively the unstuck system 10 can be activated by other motors on the well bottom.

Alternatively once the unstuck system 10 is freed from the rotation, the torsion coupling system 40 transfers the mechanical power to the unstuck system 10, i.e. for example the torque and the rpm made available by at least one of the motors on the well bottom.

Alternatively the torsion coupling system 40 allows for a complete torsional unstucking to drive the unstuck system and in general the transmission of power between the free upper part and the stuck bottom part. The coupling shall however be such as to maintain the axial connection between the two parts in order to be able to apply the traction force required for unstucking. In this axial connection it is envisaged that an elastic joint may also be included, of appropriate rigidity in order to allow the stuck bottom part to vibrate axially and independently from the free upper part, while guaranteeing the transmission of the maximum axial force required for unstucking.

Alternatively the portion free from stuck 24 comprises a drill collar 22 of the drill string 20. Alternatively the unstuck system 10 does not include thrust bearings 80 mounted above the elastic element 70.

Alternatively to the drill collar 24 these can be replaced by modules devoted to particular measures to be performed on the well bottom, jars, stabilizers.

Again alternatively it is possible to envisage that the internal rotating shaft 60 is tubular and solid, and does not allow mud to pass inside it. In this case the diameter of the internal rotating shaft 60 is much smaller than the diameter of the drill pipe 20 inside which it is mounted, so that the mud can pass between the outer wall of the internal rotating shaft 60 and the inner wall of the drill pipe 20.

An alternative system for charging the hammer 50 is that of providing for a mechanical and magnetic system comprising the internal rotating shaft 60 connected to the hammer 50 by means of a magnetic coupling which is used to define the type of motion.

Alternatively it is possible to provide for different shapes of periodic profile 65 and a number of bottom and upper portions that create discontinuities of the profile 65 allowing the cam 55 to fall downwards together with the hammer 50.

Alternatively it is also possible to provide for a number of cams 55 of the hammer 50 depending on the shape of the protruding periodic profile 65.

It is also possible to provide for a further alternative where in place of the protruding periodic profile 65 there is a periodic profile which comprises a grooved seat 65 allowing the sliding of the cam 55 of the hammer 50.

Again alternately, as shown in FIGS. 4-5, it is possible to provide for an alternative periodic axial forced vibration generator 12 which comprises a number of hammers 50 each mounted with elastic means 70.

This alternative unstuck system 10 is mounted inside a drill pipe 20 in the bottom portion 23 of the drill string 20 and comprises the internal rotating shaft 60, the number of hammers 50, the anvil element 26 and a respective number of elastic means 70 and their seats 27.

Each hammer 50 is a solid cylinder comprising a beating portion 56 of a greater diameter than an upper cylindrical portion 57 around which an elastic means 70 is mounted. Each hammer 50 comprises a cam 55. The hammers 50 are arranged around the internal rotating shaft 60 at regular intervals. Each cam 55 of the hammer 50 rises on the bottom portion of the periodic profile 65 of the rotating shaft 60 and makes the hammer move upwards, compressing the respective elastic means 70, until it reaches the upper portion of the periodic profile 65 and moves downwards once it reaches the interruption of the periodic profile 65 allowing the hammer 50 to be pushed downwards also by the thrust force of the elastic means 70. Each hammer 50 that reaches the anvil element 26 impresses an impulse and a vibration which is transmitted to the drill pipe 20 housing the unstuck system 10. Advantageously a larger number of hammers 50 allows the drill pipe 20 to vibrate several times for every rotation of the rotation shaft 60 in relation to each hammer 50 described above.

As shown in FIGS. 6-16 the periodic axial forced vibration generators 13 can be both alternative to the impulsive axial force generators 12 and complementary to the impulsive axial force generators 12 with which they can be mounted together or in series on different drill pipes 20 or on different portions of the same drill pipe on the bottom portion 23 of the drill string 20. Several axial force generators of the same kind can also be mounted.

When the periodic axial forced vibration generators 13 are mounted together with the impulsive axial force generators 12, the periodic axial forced vibration generators 13 co-operate with the impulsive axial force generators 12 to advantageously maximise the action of unstucking the stuck drill pipes 25.

Advantageously the unstuck systems 10 can comprise advantageously both impulsive axial force generators 12 and periodic axial forced vibration generators 13, as they can easily be mounted inside the drill pipes 20 on the bottom portion 23 of the drill string 20.

As shown in FIG. 6, an alternative unstuck system 10 comprises a periodic axial forced vibration generator 13 mounted inside a drill pipe 20 of the bottom portion 23 of the drill string 20 and comprises the internal rotating shaft 60, a mobile component 51, two elastic means 70 mounted on the ends of the mobile component 51, their seats 27 made in the inner walls of the drill pipe 20.

The mobile component 51 could also have a negligible mass, given that its inertia is not exploited, but rather its ability to compress or otherwise the two elastic means 70.

The mobile component 51 is tubular and concentric with the rotating shaft 60 and comprises a first hollow cylinder 52 of a first diameter comprising a through hole in which the internal rotating shaft 60 passes and a toroid 53 which extends radially from the said first hollow cylinder 52 to a second diameter greater than the first diameter. The hollow cylinder 52 and the toroid 53 are in one piece. An axial length of the first hollow cylinder 52 is greater than an axial length of the toroid 53. Between the inner wall of the drill pipe 20, an outer wall of a first end of the first hollow cylinder 52 and a first stop wall formed of the larger second diameter of the toroid 53 is a seat for the first of two elastic means 70. Between the inner wall of the drill pipe 20, an outer wall of a second end of the first hollow cylinder 52 and a second stop wall formed of the larger second diameter of the toroid 53 is a seat for the second of two elastic means 70.

The internal rotating shaft 60 comprises a periodic profile 65, preferably sinusoidal so that it advantageously has harmonic forces, cut into its own outer surface. A first cam 55 mounted integrally with an internal surface of the mobile component 51 is guided by the periodic profile 65 of the internal rotating shaft 65 so that the mobile component 51 is pushed upwards, compressing one of the two elastic means 70 and is pushed downwards by the compressed elastic means 70 to compress the second of the two elastic means 70 mounted in the opposite direction on the first hollow cylinder 52. The toroid 53 is equipped with a second cam 54 on its outer wall which extends towards the inner wall of the drill pipe 20 which houses a seat 28 for this second cam 54. Moving the mobile component 51 backwards and forwards between the compression of the first and second of the two elastic means 70, the second cam 54 mounted with the seat 28 of the drill pipe 20 transmits a translational movement to the wall of the drill pipe 20.

The unstuck system 10 of this alternative of FIG. 6 also comprises two thrust bearings 80 mounted on the ends of the respective two elastic means 70 in the seat 27 made in the inner wall of the drill pipe 20.

Depending on the type of translation imposed on the mobile component 51 the elastic force may be periodic or harmonic, with frequency also close to the resonance frequencies of the portion free from stuck 24.

Alternatively it is possible to provide for the second cam 54 and the anti-rotational system to which it is coupled with the seat 28 as described in the last alternative above, being replaced also by a geometrical coupling of a translational element which houses it, for example it is possible to provide for a first parallelepiped-shaped element slidably coupled to a second parallelepiped-shaped element, where the first element slides inside the second element. It is possible to replace these two parallelepiped-shaped elements slidably coupled to each other to obtain an anti-rotation system as described above also every time the cam is used to transform the rotational movement of the shaft 60 into a translational motion of another component, for example the hammer 50.

As shown in FIGS. 7-8, another alternative unstuck system 10 comprises an alternative periodic axial forced vibration generator 13 mounted inside a drill pipe 20 of the bottom portion 23 of the drill string 20 and comprises the internal rotating shaft 60, an annulus 90, two annular chambers 93 mounted on the axial ends of the annulus 90, two elastic means 70 mounted on the respective axial ends of the respective two annular chambers 93, seats 27 for the said elastic means 70 made in the inner walls of the drill pipe 20.

The annulus 90 is concentric with the rotating shaft 60, and is fixed to the rotating shaft 60 and rotates with it and is in flow communication with the drilled well fluid or mud present in an annulus 120, i.e. externally to the drill string 20.

The annulus 90 comprises a number of radial through openings 91 adapted to radially pass the drilled well mud through the respective radial through openings 129 in the inner walls of the drill pipe 20 through the annulus 120. Two annular chambers 93 are arranged respectively on the axial ends of the annulus 90. The two annular chambers 93 are fixed to the drill pipes 20. Each of these two chambers 93 is fitted with an axial piston 94 of the annulus 90, where this axial piston 94 is adapted to be pushed towards the elastic means 70 by the thrust of the mud penetrating into the respective annular chamber 93.

The rotating shaft 60 comprises a number of radial through openings 169 arranged radially at the annular chamber 93. The annular chamber 93 has through openings 196 on the radial through openings 169 of the rotating shaft 60. The rotation of the rotating shaft 60 allows the periodic overlapping of the radial through openings 196 in the annular chamber 93 with the corresponding radial through openings 169 in the rotating shaft 60 and therefore allow the periodic flow communication with the drilled well fluid inside the drill string 20 which passes through the rotating shaft 60.

The annulus 90 also comprises axial through openings 190 arranged in an axial direction and facing the respective two due annular chambers 93. Each annular chamber 93 comprises in turn axial through openings 199 facing the respective axial through openings 190 in the annulus 90. The axial through openings 190 of the annulus 90 in flow communication with the said radial through openings 91 which in turn are in flow communication with the said radial through openings 129 of the drill pipes which in turn are in flow communication with the annulus 120.

The flow communication and the difference in pressure of the fluid between the inside of the drill string 20 and the annular chamber 93 allow the annular chamber 93 to fill with the fluid and consequently move the axial piston 94. The axial piston 94 periodically compresses the elastic means 70 and is pushed by it. The emptying of the annular chamber 93 and the consequent contrary axial motion of the piston 94 is due to the presence of the annulus 90. The rotation of the rotating shaft 60 and therefore of the annulus 90 allows the periodic overlapping of the axial through openings 199 of the annular chamber 93 with the respective axial through openings 190 of the annulus 90 and the difference in pressure of the fluid between the inside of the annular chamber 93 and the outside 120 of the drill string 20 allows the annular chamber 93 to empty. The through openings 169, 196, 190, 199 must be suitably positioned to guarantee the correct filling and emptying of the annular chamber 93 from which the type of motion of the piston 94 depends.

As shown in FIG. 8A the mud is deviated into an upper annular chamber 93 which pushes its axial piston 94 upwards to compress the upper elastic means 70. As shown in FIG. 8B, once they reach maximum compression, the upper elastic means 70 push the upper axial piston 94 downwards, causing the upper annular chamber 93 to empty and send the mud through one of the radial through openings 91. As shown in FIG. 8C the mud at this point is pushed downwards into a bottom annular chamber 93 which pushes its piston 94 downwards to compress the bottom elastic means 70. As shown in FIG. 8D, once they reach maximum compression, the bottom elastic means 70 push the bottom axial piston 94 upwards causing the bottom annular chamber 93 to empty and send the mud through one of the radial through openings 91 in the annulus 90, continuing the oscillation which impresses impulse and vibrations directly to the drill pipe 20 where the alternative unstuck system 10 is mounted. The impressed oscillation may be periodic or harmonic.

The mud flow deviated by the annulus 90 towards the annular chambers 93 varies periodically over time with the same opening/closing law of the radial through openings 92 generating a consequent periodic variation in the pressure of the fluid inside the bottom portion of the drill string 20, caused by the periodic variation in the load losses. This internal pressure variation causes the movement of the axial pistons 94.

Again alternatively, as shown in FIGS. 9A-9C, another alternative unstuck system 10 comprises another alternative periodic axial forced vibration generator 13 mounted inside a drill pipe 20 of the bottom portion 23 of the drill string 20 and comprises two elastic means 70 mounted in seats 27 made in the inner walls of the drill pipe 20 and by two concentric annuli 95, 96 which are also concentric to the drill pipe 20 where they are mounted, i.e. an internal annulus 95 and an external annulus 96.

After the torsional freeing of the upper portion 21 of the drill string 20 it is able to rotate, while the bottom portion 23 comprises stuck drill pipes 25. The upper portion 21 comprises a lower surface which forms a sinusoidal profile 210 which, rotating, induces cams 951 of the internal annulus 95 with a circular section to follow an alternate axial movement. The cams 951 are part of the internal annulus 95 which therefore moves integrally with the cams 951. The unstuck system 10 comprises the cams 951. The torsion coupling system 40 is arranged above the unstuck system 10. The internal annulus 95 in turn forces the external annulus 96 to move alternately with a higher mass via the springs 70, for example, Wave or Belleville type springs. The external annulus 96 in turn transmits its force to the bottom portion 23 of the drill string 20. To guarantee the free vertical movement and prevent rotation the internal annulus 95 slides inside longitudinal guides.

The number of cams 951, the breadth of their oscillation induced by the rotating upper portion 21, the number of oscillations per turn, the elastic constant of the springs 70 and the main mass of the external annulus 96 are chosen to optimise the release action and if required reach the resonance of the stuck part of the string. If necessary, to limit the size of the external annulus 96 which represents the mass in movement, a metal of a high specific weight such as tungsten can be used.

Alternatively, an alternative shaft 60 comprises the sinusoidal profile 210 described in the preceding alternative.

Again alternatively, as shown in FIGS. 10A-10C another alternative unstuck system 10 comprises another alternative periodic axial forced vibration generator 13, where the upper portion 21 of the drill string 20 in rotation and the rotating shaft 60 comprise at least a cam 601 which, via a coupling with a sinusoidal profile 952 of the internal annulus 95, forces the internal annulus 95 of an appropriate mass to follow an alternative, preferably, sinusoidal periodic axial path. FIGS. 10A-10C show a cam 601, but there could also be two or more cams 601. The unstuck system 10 comprises the cams 601 and the sinusoidal profile 952. The alternative torsion coupling system 40 is positioned above the said unstuck system 10. The mass of this internal annulus 95 placed in rapid movement generates a force of inertia which is discharged via the cams 952 on the bottom portion 23 of the drill string 20. The transformation from rotating motion to axial motion takes place with radial friction so the system must be appropriately lubricated. To guarantee the free vertical movement and prevent rotation, the internal annulus 95 is forced into rotation by means of the rotating shaft 60 via longitudinal guides in which the internal annulus 95 slides. The number of cams 952, the breadth of their oscillation induced by the rotating shaft 60, the number of oscillations per turn and the main mass of the internal annulus 95 are chosen to optimise the release action and if required reach the resonance frequency ν₀ of the portion free from stuck 24. If necessary, to limit the size of the external annulus 96 which represents the mass in movement, a metal of a high specific weight such as tungsten can be used.

Again alternatively, referring to the alternative shown in FIGS. 10A-10C, depending on how the torsion coupling system 40 is made, the cam 601 could be made alternatively on the external annulus 96 so that the rapid movement of the mass of the internal annulus 95 generates a force of inertia which is discharged via the cam 601 directly on the bottom portion 23 of the drill string 20. The components presented on a certain part of the cam coupling 601 and 952 can therefore be made independently on one component or its complementary component.

A further alternative shown in FIGS. 11A-11C representing an alternative unstuck system 10 comprises an alternative periodic axial forced vibration generator 13, where the upper portion 21 of the drill string 20 comprises four or more toothed cams 602 which, coupled to a rack 953 in the main mass of the internal annulus 95, forces the mass itself, of a cylindrical crown shape, to follow a preferably sinusoidal alternate periodic axial path. The unstuck system 10 comprises the toothed cams 602 and the rack 953. The mass of this internal annulus 95 placed in rapid movement generates a force of inertia which is discharged via the cams 602 and thus on the bottom portion 23 of the drill string 20. The coupling of the toothed wheels 602 and rack 953 could also be of a different type provided it guarantees the continuity of movement without sliding of the cams 602 themselves. The advantage over the alternative solution shown in FIGS. 10A-10C is that the transformation between rotational and alternate axial motion would occur without radial friction, but only with rolling resistance and would therefore allow for higher rotational speeds with consequent greater alternate axial loads. The breadth of the oscillations could also be greater. Half of the cams 602 are occupied by the upper rack 953 and half by the bottom rack 953. The number of cams 602 may be higher than four for high expected loads and in any case divided into two groups, half occupying the upper rack 953 and half the bottom rack 953. To guarantee the free vertical movement and prevent rotation the internal annulus 95 slides inside longitudinal guides. The breadth of the oscillation induced by the rotating shaft 60, the number of oscillations per turn and the main mass of the internal annulus 95 are chosen to optimise the release action and if required reach the resonance frequency of the portion free from stuck 24.

Again alternatively, referring to the alternative shown in FIGS. 11A-11C, depending on how the torsion coupling system 40 is made, the cam 602 could be made alternatively on the rotating shaft 60 so that the rapid movement of the mass of the internal annulus 95 generates a force of inertia which is discharged via the cam 602 directly on the drill string 20. The components presented on a certain part of the cam coupling 602 and 953 can therefore be made independently on one component or its complementary component.

Another alternative again is shown in FIGS. 12A-12D which represent another alternative unstuck system comprising an alternative periodic axial forced vibration generator 13, where the bottom surface 210 of the upper portion 21 of the drill string 20 in rotation comprises a sinusoidal profile 210 along which the rotating elements 600 slide, which may be cylinders or balls. The alternative unstuck system 10 comprises the rotating elements 600 and the preferably sinusoidal periodic profile 210. During the rotating movement this profile 210, via the rotating elements 600, transmits a preferably sinusoidal, but not only, alternate axial force to the internal annulus 95 which when moving compresses a spring 70.

The axial movement of the internal annulus 95 could also be non-sinusoidal, and become more impulsive, it this could offer greater effectiveness in the release action.

The advantage of this alternative is mainly linked to the simplicity of use of rotating elements which therefore have rolling resistance.

Yet another alternative is shown in FIGS. 13A-13C and in FIGS. 14A-14E, representing another alternative unstuck system 10 comprising an alternative periodic axial forced vibration generator 13, where the upper portion 21 of the drill string 20 comprises a series of magnetic elements of the same pole positioned on the same circular section. With this cylinder the internal annulus 95 is free to slide axially and can move only axially inside some axial guides. Two series of magnets with alternating polarity are positioned on the inner wall of this internal annulus 95. The alternative unstuck system 10 comprises the series of magnets. In relation to the series of magnets fitted in the inner wall of the rotating shaft 60, one series of magnets is positioned slightly higher and one slightly lower. When the rotating shaft 60 rotates its magnets interact with the magnet inside the internal annulus 95 generating an alternate axial force as in each position the central magnet is pushed away by one and attracted by the other. This force is used to compress two cylindrical springs 70 on the axial ends of the internal annulus 95 transmitting the force to the stuck drill pipes 25. Advantageously the connection between the internal annulus 95 and the bottom portion 23 of the drill string 20 is not of the mechanical type and therefore there is no mechanical friction. The number of magnets on the rotating shaft 60 can be chosen to increase the overall force, while the number of alternate magnets on the internal annulus 95 should be chosen to optimise the frequency of the oscillations and ensure for example that the system can reach the resonance frequencies of the portion free from stuck 24. The distance between the two series of magnets, the intensity of the magnetic field and the type of magnets can be chosen to maximise the action. If the forces generated by the system are not very high, more than one magnetic coupling can be included.

Another alternative is shown in FIGS. 15A-15C representing another alternative unstuck system 10 comprising an alternative periodic axial forced vibration generator 13, where the upper portion 21 of the drill string 20 in its connection with the stuck drill pipes 25 comprises cylindrical cams 603 which during rotation transfer a direct axial movement thanks to a curved profile 961 of an alternate shape made in the external annulus 96.

It is also possible to provide for the cylindrical cams 603 and the curved profile 961 being mounted on respective complementary elements.

The alternative unstuck system 10 comprises cylindrical inserts 603 and the curved profile 961.

When there are no stuck drill pipes 25 and the unstuck system 10 is disabled, then there is no relative movement between the two parts and the cams are not used. When on the other hand there are stuck drill pipes 25 the system is activated and there can be relative rotation between the top part fixed to the pipes free to rotate 21, and the bottom part fixed to the stuck drill pipes 25. When the cams slide within the curved profile 961 made in the external annulus 96, a relative oscillating movement between the two parts, which induces axial forces which promote to detachment of the stuck drill pipes 25.

This profile 961 may be sinusoidal or another shape for a different type of movement. Advantageously springs are not used but the elasticity of the rotating shaft 60 represents the equivalent elastic element. The breadth of oscillation, generated by the axial height of the sinusoidal profile 961 will be minimal as contrary to the preceding alternative cases the involved mass is very high. However even with minimum breadth the transmitted axial force could be very high, precisely due to the direct coupling. Consequently the action applied could be very effective in unstucking the stuck drill pipes 25. The number of oscillations per turn, the breadth of the oscillations, the shape of the profile 961 and the number of circular inserts 603 are variable, in order to optimise the effectiveness of the release action.

Yet another alternative is shown in FIGS. 16A-16C representing another alternative unstuck system 10 comprising an alternative periodic axial forced vibration generator 13, where the upper portion 21 of the drill string 20 comprises on a lower end a series of cylindrical or spherical rotating inserts 603.

When there are no stuck drill pipes 25 and the unstuck system 10 is disabled there is no relative movement and the inserts do not rotate. When there are stuck drill pipes 25 the system 10 is activated and the relative rotation between the upper part of the unstuck system 10 fixed to the drill string 21 and the bottom part fixed to the stuck drill pipes 25 generates axial oscillations between the two parts due to the rotation of the cylinders or spheres 603 along the sinusoidal or other shaped profile 961.

The alternative unstuck system 10 comprises the rotating cylindrical inserts 603 and the profile 961. The movement from rotary to axial occurs by rolling resistance and can advantageously offer greater transmitted forces. To allow free movement, every cylindrical or spherical support rotates resting on only one profile and the number of inserts must be chosen in order to share the load applied to the maximum possible number of inserts, remembering that, after being released, these inserts must also support the maximum traction of the drill string 20 during the release phases. To facilitate the load supported between the two series of rotating inserts the external annulus 96 may be positioned as a support for both. In this case the annulus 96 would rotate at a double angular speed. The number of oscillations per turn, the breadth of the oscillations, the shape of the profile and the number of circular inserts are variable and this optimises the effectiveness of the release action.

As regards the operation of the unstuck system 10, a process is defined for unstucking stuck drill pipes 25 of a drill string 20 of a drilling apparatus 100 adapted to drilled wells to extract fluids or mud, where said drill string 20 comprises a top portion 21 and a bottom portion 23 comprising said stuck drill pipes 25 stuck by a soil surrounding a sunk well. The process comprises a first operation of disconnecting the top portion 21 from the bottom portion 23 of the drill string 20 when there are stuck drill pipes 25 by means of a torsion coupling system 40.

The process comprises a second operation of transferring a rotation to the unstuck system 10 by means of the torsion coupling system 40 after the top portion 21 has been released from the bottom portion 23 of the drill string 20.

The procedure comprises a third operation of generating axial forced vibrations by means of at least one forced vibration generator 11, 12, 13 of the unstuck system 10, where the said at least one axial forced vibration generator 11, 12, 13 comprises at least one axially movable element 50, 51, 94, 95, 96.

The third operation comprises a generation of at least one vibration in a band of frequencies ν_(A) by said at least one axially moveable element 50, 51, 94, 95, 96.

The third operation comprises in succession a propagation of said at least one drill pipe 20 vibration of a portion free from stuck 24 of the bottom portion 23 of the drill string 20 which is comprised between the torsion coupling system 40 and the stuck drill pipes 25, where the vibrations induced in the portion free from stuck 24 are comprised in a band of induced frequencies ν_(F) close or corresponding to a resonance frequency ν₀ of the portion free from stuck 24.

The said third operation comprises in succession that said induced vibrations propagate in the stuck drill pipes 25 and from here to the surrounding soil.

Advantageously the unstuck system 10 can be promptly activated, immediately after at least one drill pipe 25 has stuck.

Advantageously there is an increase in operational safety as actions linked to the removal of the drill string and the use of the retrieval string are avoided.

Advantageously the unstuck system 10 generating axial stresses can also act at the same time to operate a similar device devoted to the generation of other types of forces such as flexural and/or torsional forces. Moreover its action may be added to any other external action acting on the drill string and/or generated by the portion of the string that is free to rotate, after activating the torsion coupling system 40.

The invention thus conceived is susceptible to numerous modifications and variations, all falling within the same inventive concept; furthermore, all details can be replaced by equivalent technical elements. In practice, the materials used, as well as the dimensions, can be of any type according to the technical requirements. 

1-20. (canceled)
 21. An unstuck system for stuck drill pipes of a drill string of a drilling apparatus adapted to drilled wells to extract fluids or mud, wherein said drill string comprises a top portion and a bottom portion comprising at least one drill pipe susceptible of being stuck by a soil surrounding a sunk well, and a torsion coupling system adapted to release the top portion from the bottom portion of the drill string when there are stuck drill pipes being stuck, and said unstuck system is associated with said torsion coupling system such that once the top portion is released from the bottom portion of the drill string the torsion coupling system transfers a rotation to the unstuck system, said unstuck system comprising at least one forced vibration generator comprising at least one axially movable element adapted to generate at least one vibration that propagates to a portion free from being stuck of the bottom portion of the drill string comprised between the torsion coupling system and the stuck drill pipes, vibrations induced in the portion free from being stuck are comprised in a band of induced frequencies close or corresponding to a resonance frequency of the portion free from being stuck, said induced vibrations propagate in the stuck drill pipes and into the surrounding soil.
 22. The unstuck system according to claim 21, wherein said portion free from stuck comprises drill collars of the drill string.
 23. The unstuck system according to claim 22, wherein said torsion coupling system transfers the rotation to the unstuck system by means of a rotating shaft comprising a grooved profile which is connected to the torsion coupling system.
 24. The unstuck system according to claim 23, wherein the rotating shaft comprises at least one interrupted periodic profile, and the unstuck system comprises said at least one axially moveable element which is at least one hammer mounted with at least one elastic means of the unstuck system, said at least one hammer is slidably mounted in an axis with a drill pipe of the bottom portion of the drill string, said at least one hammer comprises at least one cam which is guided in rotation by said periodic profile, such that said at least one hammer is periodically adapted to compress said at least one elastic means and to be pushed by said at least one elastic means along the axis of the drill string, and a second drill pipe lower than the drill pipe comprises at least one anvil element adapted to be struck by said at least one hammer.
 25. The unstuck system according to claim 24, wherein said at least one hammer is a single hammer which is a hollow cylinder concentric with said rotating shaft, and said single hammer comprises said at least one cam.
 26. The unstuck system according to claim 24, wherein said at least one hammer is a multiplicity of hammers, each of which comprises at least one cam, and said multiplicity of hammers is arranged around said rotating shaft.
 27. The unstuck system according to claim 23, wherein said at least one axially moveable element is at least one tubular movable component concentric with said rotating shaft, and comprises at least one cam adapted to be guided by at least one periodic profile of the rotating shaft, and two elastic means are mounted at two axial ends of said at last one movable component, such elastic means being adapted to be periodically compressed by said at least one movable component and to push said at least one movable component.
 28. The unstuck system according to claim 27, wherein said at least one movable component comprises at least one second cam mounted with a seat of a drill pipe to transmit translational movement to said drill pipe.
 29. The unstuck system according to claim 27, wherein said at least one periodic profile comprises a bottom portion and a top portion at a height level higher than the bottom portion.
 30. The unstuck system according to claim 23, comprising an annulus concentric and integral with the rotating shaft and in flow communication with a well drilling fluid, at least one annular chamber arranged at one of two axial ends of the annulus, wherein said at least one axially moveable element is a piston of said annular chamber, and said at least one piston is adapted to periodically compress at least one elastic means and to be pushed by the at least one elastic means.
 31. The unstuck system according to claim 30, wherein said annular chamber comprises at least one first radial through opening, and said rotating shaft comprises at least one second radial through opening in flow communication with the well drilling fluid flowing inside the rotating shaft, during the rotation of the rotating shaft said at least one second radial through opening of the rotating shaft is at said at least one first through opening of the annular chamber being adapted to let the fluid pass towards said at least one annular chamber to move said at least one piston.
 32. The unstuck system according to claim 31, wherein said annulus comprises at least one third radial through opening adapted to let the fluid pass from inside the drill pipe to outside of the drill pipe, at least one first axial through opening in flow communication with at least one second axial through opening of said at least one annular chamber, where said at least one first axial through opening of said annulus is in flow communication with said at least one third radial through opening of said annulus.
 33. The unstuck system according to claim 30, wherein said rotating shaft is tubular and hollow adapted to let the well drilling fluid pass.
 34. The unstuck system according to claim 21, comprising at least one cam and at least one gear-shaped or sinusoidal-shaped or curvilinear-shaped profile, wherein at least one axially moveable element of the axial forced vibration generator is at least one annulus concentric with a drill pipe where the at least one annulus is mounted.
 35. The unstuck system according to claim 34, wherein said at least one axially moveable element of the axial forced vibration generator comprises two annuli concentric with each other.
 36. The unstuck system according to claim 34, wherein said at least one annulus comprises said at least one cam and said top portion of the drill string comprises said at least one gear-shaped or sinusoidal-shaped or curvilinear-shaped profile.
 37. The unstuck system according to claim 34, wherein said at least one annulus comprises said at least one gear-shaped or sinusoidal-shaped or curvilinear-shaped profile, and said top portion of the drill string comprises said at least one cam.
 38. The unstuck system according to claim 21, comprising a series of magnets, wherein at least one axially moveable element of the axial forced vibration generator is at least one annulus with a drill pipe where the at least one annulus is mounted, where said series of magnets are mounted with at least one of said bottom portion of the drill string and one of said at least one annulus.
 39. The unstuck system according to claim 21, comprising at least one thrust bearing mounted at ends of said at least one elastic means of the unstuck system, where said at least one elastic means is mounted with said at least one axially moveable element.
 40. A process for unstucking stuck drill pipes of a drill string of a drilling apparatus adapted to drilled wells to extract fluids or mud, wherein said drill string comprises a top portion and a bottom portion comprising said drill pipes stuck by a soil surrounding a sunk well, said process comprising: disconnecting the top portion from the bottom portion of the drill string when there are stuck drill pipes by means of a torsion coupling system; transferring a power to the unstuck system by means of the torsion coupling system after the top portion has been released from the bottom portion of the drill string; and generating axial forced vibrations by means of at least one forced vibration generator of the unstuck system according to claim 21, where said at least one axial forced vibration generator comprises at least one axially moveable element, wherein the generating comprises a generation of at least one vibration by said at least one axially moveable element, the generating comprises in succession a propagation of said at least one drill pipe vibration of a portion free from being stuck of the bottom portion of the drill string which is comprised between the torsion coupling system and the stuck drill pipes, where the vibrations induced in the portion free from being stuck are comprised in a band of induced frequencies close or corresponding to a resonance frequency of the portion free from being stuck, and the generating comprises in succession that said induced vibrations propagate in the stuck drill pipes and into the surrounding soil. 